package com.example.socket.server.nio;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.util.Iterator;
import java.util.Set;

public class NioSelectorServer {

    public static void main(String[] args) throws IOException {
        //创建NIO ServerSocketChannel
        ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
        serverSocketChannel.socket().bind(new InetSocketAddress(9000));
        //设置ServerSocketChannel为非阻塞
        serverSocketChannel.configureBlocking(false);
        //打开Selector处理channel ，即创建epoll
        Selector selector = Selector.open();
        //把ServerSocketChannel 注册到Selector上，并且selector对客户端accept连接操作感兴趣
        serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
        System.out.println("服务端启动成功");
        while (true){
            //阻塞等待需要处理的事件法伤
            selector.select();
            //获取selector种注册的全部事件的SelecctionKey实例
            Set<SelectionKey> selectionKeys = selector.selectedKeys();
            Iterator<SelectionKey> iterator = selectionKeys.iterator();
            //遍历selectionKey对事件进行处理
            while (iterator.hasNext()){
                System.out.println("===================");
                SelectionKey key = iterator.next();
                //如果是OP_ACCEPT事件，则进行连接获取和事件注册
                if(key.isAcceptable()){
                    ServerSocketChannel server = (ServerSocketChannel) key.channel();
                    SocketChannel socketChannel = server.accept();
                    socketChannel.configureBlocking(false);
                    //这里只注册了读事件，如果需要给客户端发送数据可以注册写事件
                    socketChannel.register(selector,SelectionKey.OP_READ);
                    System.out.println("客户端连接成功");
                    //如果是OP_READ事件，则进行读取和打印
                }else if(key.isReadable()){
                    SocketChannel socketChannel = (SocketChannel) key.channel();
                    ByteBuffer byteBuffer = ByteBuffer.allocate(6);
                    int len = socketChannel.read(byteBuffer);
                    //如果有数据，把数据打印出来
                    if(len >0 ){
                        System.out.println("接收到消息："+new String(byteBuffer.array(),0,len,"GBK"));
                        //如果客户端断开连接，关闭Socket
                    }else if (len == -1){
                        System.out.println("客户端断开连接");
                        socketChannel.close();
                    }
                }
                //从事件集合里删除本次处理的key，防止下次select 重复处理
                iterator.remove();
            }
        }
    }
}
